Showing papers in "Inorganic Chemistry in 2010"
TL;DR: A review of the oxygen reduction reaction and its use in fuel-cell applications is presented and mechanisms of the ORR and implementations of catalysts for this reaction are discussed.
Abstract: A review of the oxygen reduction reaction (ORR) and its use in fuel-cell applications is presented. Discussed are mechanisms of the ORR and implementations of catalysts for this reaction. Specific catalysts discussed include nanoparticles, macrocycles and pyrolysis products, carbons, chalcogenides, enzymes, and coordination complexes. A prospectus for future efforts is provided.
623 citations
TL;DR: A significantly improved catalyst, Re(bipy-tBu)(CO)(3)Cl (4), for the reduction of carbon dioxide to carbon monoxide was found and shows two one-electron reductions under argon, one reversible at -1445 mV (vs SCE), and one irreversible at -1830 mV.
Abstract: Five Re(bipy)(CO)(3)Cl complexes were prepared and studied where bipy was 4,4'-dicarboxyl-2,2'-bipyridine (1), 2,2'-bipyridine (2), 4,4'-dimethyl-2,2'-bipyridine (3), 4,4'-di-tert-butyl-2,2'-bipyridine (4), and 4,4'-dimethoxy-2,2'-bipyridine (5). From this group, a significantly improved catalyst, Re(bipy-tBu)(CO)(3)Cl (4), for the reduction of carbon dioxide to carbon monoxide was found. The complex shows two one-electron reductions under argon, one reversible at -1445 mV (vs SCE), and one irreversible at -1830 mV. Under CO(2) the second irreversible wave displays a large catalytic enhancement in current. Diffusion coefficients were determined using the Levich-Koutecky method (1.1 × 10(-5) cm(2)/s for the neutral complex and 8.1 × 10(-6) cm(2)/s for the singly reduced species), and a second order rate constant for the electrochemical reduction with CO(2) of 1000 M(-1) s(-1) was measured. Bulk electrolysis studies were performed to measure Faradaic efficiencies for the primary gaseous products, η(CO) = 99 ± 2% in acetonitrile.
461 citations
TL;DR: The half-wave potential is proposed as reference potential for the determination of overpotential values for H(2)-evolving catalysts in non-aqueous solvents and the formulas to which the measured potential should be compared are derived, taking into account the effect of homoconjugation.
Abstract: In an effort to standardize the determination of overpotential values for H2-evolving catalysts in non-aqueous solvents and allow a reliable comparison of catalysts prepared and assayed by different groups, we propose to adopt the half-wave potential as reference potential. We provide a simple method for measuring it from usual stationary cyclic voltammograms, and we derive the formulas to which the measured potential should be compared, taking into account the effect of homoconjugation. We also revisit tabulated values of the standard reduction potential of protons in non-aqueous solvents, EH+/H2°.
351 citations
TL;DR: Investigations show further that the emission properties of Ir(ppy)(3) depend distinctly on the complex's environment or the matrix cage according to distinct changes of spin-orbit coupling effectiveness and have consequences for optimizations of the material's properties if applied as an organic light-emitting diode (OLED) emitter.
Abstract: The emitting triplet state of fac-Ir(ppy)3 (fac-tris(2-phenylpyridine)iridium) is studied for the first time on the basis of highly resolved optical spectra in the range of the electronic 0−0 trans...
322 citations
TL;DR: This presentation provides a review of the author's research group's contributions to the organometallic chemistry of carbon dioxide with a focus on incorporating this information into the development of an effective means for producing chemicals from this greenhouse gas.
Abstract: This presentation provides a review of the author’s research group’s contributions to the organometallic chemistry of carbon dioxide with a focus on incorporating this information into the development of an effective means for producing chemicals from this greenhouse gas. The types of chemistry addressed include insertion reactions of CO2 into M−H, M−C, and M−O bonds as well as seminal contributions related to the copolymerization reactions of CO2 and cyclic ethers. Relevant to this latter subject, efforts were made to place the author’s achievements into perspective with the accomplishments of other investigators, but these efforts were not meant to be exhaustive.
304 citations
TL;DR: This new material is a very promising NLO crystal for practical application in the IR region and exhibits a second harmonic generation response at 1 μm that is approximately 2-3 times that of the benchmark material AgGaS(2).
Abstract: The new compound BaGa(4)Se(7) has been synthesized for the first time. It crystallizes in the monoclinic space group Pc with a = 7.6252 (15) A, b = 6.5114 (13) A, c = 14.702 (4) A, β = 121.24 (2)°, and Z = 2. In the structure, GaSe(4) tetrahedra share corners to form a three-dimensional framework with cavities occupied by Ba(2+) cations. The material is a wide-band gap semiconductor with the visible and IR optical absorption edges being 0.47 and 18.0 μm, respectively. BaGa(4)Se(7) melts congruently at 968 °C and exhibits a second harmonic generation response at 1 μm that is approximately 2-3 times that of the benchmark material AgGaS(2). A first-principles calculation of the electronic structure, linear and nonlinear optical properties of BaGa(4)Se(7) was performed. The calculated birefractive indexΔn = 0.08 at 1 μm and the major SHG tensor elements are: d(11) = 18.2 pm/V and d(13) = -20.6 pm/V. This new material is a very promising NLO crystal for practical application in the IR region.
297 citations
TL;DR: The obtained phosphor exhibits a strong excitation band between 250 and 430 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip.
Abstract: A novel white-light-emitting phosphor Ca9Lu(PO4)7:Eu2+,Mn2+ has been prepared by solid-state reaction. The photoluminescence properties indicate that there is an efficient energy transfer from the Eu2+ to Mn2+ ions via a dipole−quadrupole reaction. The obtained phosphor exhibits a strong excitation band between 250 and 430 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Upon excitation of UV light, white light is realized by combining a broad blue-green emission band at 480 nm and a red emission band at 645 nm attributed to the Eu2+ and Mn2+ ions. The energy-transfer efficiency and critical distance were also calculated. Furthermore, the phosphors can generate lights from blue-green through white and eventually to red by properly tuning the relative ratio of the Eu2+ to Mn2+ ions through the principle of energy transfer. Preliminary studies showed that the phosphor might be promising as a single-phased white-light-emitting phosphor for a UV white-light LED.
289 citations
TL;DR: A series of monomeric ruthenium polypyridyl complexes have been synthesized and characterized, and their performance as water oxidation catalysts has been evaluated.
Abstract: A series of monomeric ruthenium polypyridyl complexes have been synthesized and characterized, and their performance as water oxidation catalysts has been evaluated. The diversity of ligand environments and how they influence rates and reaction thermodynamics create a platform for catalyst design with controllable reactivity based on ligand variations.
286 citations
TL;DR: A conformationally constrained (coumarin-pyrrolidinyl-triazolyl-bipyridyl) fluoroionophore conjugate was synthesized through click chemistry and exhibited a high association constant with submicromolar detection for the aluminum ion.
Abstract: A conformationally constrained (coumarin−pyrrolidinyl−triazolyl−bipyridyl) fluoroionophore conjugate was synthesized through click chemistry. The fluoroionophore serves as a selective chemosensor for Al3+ based on internal charge transfer. The coumarin−bipyridyl chemosensor exhibited a high association constant with submicromolar detection for the aluminum ion.
276 citations
TL;DR: The post-aging of as-grown hematite nanocry crystals in alcohol and distilled water has been described and both vibration spectroscopy and electronic spectra of these nanocrystals with a continuing shape change show a highly shape-dependent nature.
Abstract: Uniform hexagonal hematite (α-Fe2O3) nanoplates have been synthesized by a facile alcohol-thermal reaction, and a new nanostructure of α-Fe2O3 has been proposed. Each nanoplate is enclosed by (0001) basal planes and {1012} side surfaces. The phase, size, shape, and growth orientation of these nanocrystals were characterized by powder X-ray diffraction and electron microscopy. The thickness and diameter of these nanocrystals could be finely tuned by the selective use of alcohol solvent with increasing carbon atom number in the linear alkyl chain. A variety of nanocrystals with systemically changeable shapes from nanoplates to nanograins have been obtained. Specific adsorption of alcohol molecules on polar (0001) facets is proposed to be the main issue to modify the growth behavior of hematite nanocrystals. The presence of distilled water and the addition of sodium acetate have also been investigated. Either of them has a great influence on the growth of hematite nanocrystals, and shape-controlled growth c...
270 citations
TL;DR: It is revealed that mesoporous materials such as PCN-100 can be applied in the elimination of heavy metal ions from waste liquid, and both PCNs-100 and -101 exhibit size-selective catalytic activity toward the Knoevenagel condensation reaction.
Abstract: By using Zn4O(CO2)6 as secondary building units (SBUs) and two extended ligands containing amino functional groups, TATAB and BTATB (TATAB = 4,4′,4′′-s-triazine-1,3,5-triyltri-p-aminobenzoate and BTATB = 4,4′,4′′-(benzene-1,3,5-triyltris(azanediyl))tribenzoate), two isostructural mesoporous metal−organic frameworks (MOFs) with cavities up to 2.73 nm, designated as PCN-100 and PCN-101 (PCN represents porous coordination network), have been synthesized. N2 sorption isotherms of both PCN-100 and -101 showed typical type IV behavior, indicating their mesoporous nature. The TATAB ligand that comprises PCN-100 was employed to capture heavy metal ions (Cd(II) and Hg(II)) by constructing complexes within the pores with a possible coordination mode similar to that found in aminopyridinato complexes. This reveals that mesoporous materials such as PCN-100 can be applied in the elimination of heavy metal ions from waste liquid. In addition, both PCNs-100 and -101 exhibit size-selective catalytic activity toward the K...
TL;DR: Nine new coordination polymers, namely, Mn(2)(L)(H(2)O)(4)O, Zn(5)(L))(2)(mu(3)-O)(2)], and 9, containing tetranuclear Cd(II) clusters, have been synthesized under hydrothermal conditions and display a rare trinodal (3,4,7)-connected network.
Abstract: Nine new coordination polymers, namely, [Mn2(L)(H2O)4]·H2O (1), [Cd(L)0.5(H2O)] (2), [Zn5(L)2(μ3-O)2(H2O)4]·2H2O (3), [Zn4(L)2(μ3-O)2][Zn(H2O)5]·2H2O (4), [Zn2(L)(biim-4)0.5(H2O)3]·H2O (5), [Cd2(L)(bpy)(H2O)]·2H2O·0.5(CH3CH2OH) (6), [Cu2(H2L)2(bpy)2] (7), [Cu2(L)(bpy)(H2O)] (8), and [Cu2(L)(bpy)1.5(H2O)2.5] (9), where H4L = 1,2,3,4-benzenetetracarboxylic acid, biim-4 = 1,1′-(1,4-butanediyl)bis(imidazole), and bpy = 4,4′-bipyridine, have been synthesized under hydrothermal conditions. Compound 1 displays a rare trinodal (3,4,7)-connected (42·6)(45·6)(47·68·86) topology. 2 possesses an α-Po net. 3 is a novel 3D framework based on pentanuclear ZnII clusters. By adjustment of the pH values of the reaction mixture of 3 with a Na2CO3 solution, a structurally different compound, 4, was obtained, which exhibits a 3D porous framework with the [Zn(H2O)6]2+ cations located in the channels. 5 is an unusual example of a trinodal (3,5)-connected network with a Schlafli symbol of (42·6)(62·8)(42·62·85·10), whereas 6, co...
TL;DR: It is found that 2,2'-bipyridine N,N'-dioxide is produced when 1b is subject to excess Ce(IV) in acidic media, which suggests that dissociation of the bpy ligand is a source of catalyst deactivation and/or decomposition.
Abstract: A family of compounds based on the mononuclear coordination complex [Ru(tpy)(bpy)(OH2)]2+ (1b; tpy = 2,2′:6′,2′′-terpyridine, bpy = 2,2′-bipyridine) are shown to be competent catalysts in the Ce(IV)-driven oxidation of water in acidic media. The systematic installation of electron-withdrawing (e.g., −Cl, −COOH) and −donating (e.g., −OMe) groups at various positions about the periphery of the polypyridyl framework offers insight into how electronic parameters affect the properties of water oxidation catalysts. It is observed, in general, that electron-withdrawing groups (EWGs) on the bpy ligands suppress catalytic activity (kobs) and enhance catalytic turnover numbers (TONs); conversely, the presence of electron-donating groups (EDGs) accelerate catalytic rates while decreasing catalyst stability. We found that 2,2′-bipyridine N,N′-dioxide is produced when 1b is subject to excess Ce(IV) in acidic media, which suggests that dissociation of the bpy ligand is a source of catalyst deactivation and/or decomposi...
TL;DR: In this Forum Article, several biological and synthetic examples are presented and discussed in terms of structure-function relationships and particular emphasis is given to systems with defined noncovalent interactions, such as intramolecular H-bonds involving dioxygen-derived ligands.
Abstract: Alfred Werner proposed nearly 100 years ago that the secondary coordination sphere has a role in determining the physical properties of transition-metal complexes. We now know that the secondary coordination sphere impacts nearly all aspects of transition-metal chemistry, including the reactivity and selectivity in metal-mediated processes. These features are highlighted in the binding and activation of dioxygen by transition-metal complexes. There are clear connections between control of the secondary coordination sphere and the ability of metal complexes to (1) reversibly bind dioxygen or (2) bind and activate dioxygen to form highly reactive metal−oxo complexes. In this Forum Article, several biological and synthetic examples are presented and discussed in terms of structure−function relationships. Particular emphasis is given to systems with defined noncovalent interactions, such as intramolecular H-bonds involving dioxygen-derived ligands. To further illustrate these effects, the homolytic cleavage o...
TL;DR: The highly structured emission spectra, long life times, and DFT calculations suggested that the emissive state is primarily a (3)LC state with metal-to-ligand charge-transfer (MLCT) admixture.
Abstract: N,N-Di(6-phenylpyridin-2-yl)aniline (L1), N,N-di(6-(2,4-difluorophenyl)pyridin-2-yl)aniline (L2), N,N-di(3-(pyridin-2-yl)phenyl)aniline (L3), N,N-di(3-(1H-pyrazol-1-yl)phenyl)aniline (L4), N,N-di(3-(3-methyl-1H-pyrazol-1-yl)phenyl)aniline (L5), and N,N-di(3-(4-methyl-1H-pyrazol-1-yl)phenyl)aniline (L6) undergo cyclometalation to produce two types of tetradentate bis-cyclometalated platinum(II) complexes: C∧N*N∧C platinum complexes 1 and 2 and N∧C*C∧N platinum complexes 3−6, respectively, where an “X∧Y” (X, Y = C or N) denotes a bidentate coordination to the platinum to form a five-membered metallacycle and “X*Y” denotes a coordination to form a six-membered metallacycle. The crystal structures of 1, 3, and 5 were determined by the single-crystal X-ray diffraction analysis, showing distorted square-planar geometry, that is, two C∧N coordination moieties are twisted. Complex 5 showed much greater distortion with largest deviation of 0.193 A from the mean NCCNPt coordination plane, which is attributed to the...
TL;DR: Magnetic properties indicate that carboxyl group of 2-furoate mediates different magnetic couplings in light and heavy rare earth complexes, namely, antiferromagnetic interaction between light rare earth ions and ferromagnetic interactions between heavy ones.
Abstract: A series of one-dimensional complexes [Ln(L1)3(HOCH2CH2OH)]n (L1 = 2-furoate anion; Ln = Nd (1), Sm (2), Gd (3), Tb (4), Dy (5), Er (6)) have been synthesized. The complexes were crystallized in the monoclinic space group P2(1)/c and show a chain-like structure determined by single-crystal X-ray diffraction. Magnetic properties indicate that carboxyl group of 2-furoate mediates different magnetic couplings in light and heavy rare earth complexes, namely, antiferromagnetic interaction between light rare earth ions and ferromagnetic interaction between heavy ones. Noticeably, complex 5 displays a strong frequency dependence of alternating current (AC) magnetic properties. Further magnetic studies show a distribution of a single relaxation process in 5. While 1,10-phenanthroline and phthalate anion (L2) were employed, [Dy2(L2)6(H2O)]n (7) was isolated by hydrothermal reactions and characterized magnetically. Research results also show the frequency dependence of AC magnetic susceptibilities, although the pht...
TL;DR: A mononuclear ruthenium complex, Ru(II)L(pic)(2) (1) (H(2)L = 2,2'-bipyridine-6,6'-dicarboxylic acid; pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system.
Abstract: Discovery of an efficient catalyst bearing low overpotential toward water oxidation is a key step for light-driven water splitting into dioxygen and dihydrogen. A mononuclear ruthenium complex, Ru(II)L(pic)2 (1) (H2L = 2,2′-bipyridine-6,6′-dicarboxylic acid; pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system composed of a photosensitizer, sacrificial electron acceptor, and complex 1. The detailed electrochemical properties of 1 were studied, and the onset potentials of the electrochemically catalytic curves in pH 7.0 and pH 1.0 solutions are 1.0 and 1.5 V, respectively. The low catalytic potential of 1 under neutral conditions allows the use of [Ru(bpy)3]2+ and even [Ru(dmbpy)3]2+ as a photosensitizer for photochemical water oxidation. Two different sacrificial electron acceptors, [Co(NH3)5Cl]Cl2 and Na2S2O8, were used to generate the oxidized state of ruthenium tris(2,2′-bipyridyl...
TL;DR: The ability to generate YVO(4) nano/microstructures with diverse shapes, multicolor emission, and higher quantum efficiency provides a great opportunity for systematically evaluating their luminescence properties, as well as fully exploring their applications in many types of color display fields.
Abstract: YVO4 nano/microcrystals with multiform morphologies, such as nanoparticles, microdoughnut, micropancake, pillar structure, and microflower, have been synthesized via a facile hydrothermal route. A series of controlled experiments indicate that the shape and size of as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as reaction time, vanadium sources, different organic additives, and the molar ratio of organic additive trisodium citrate (Cit3−):Y3+. It is found that Cit3− as a ligand and shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of various geometries of the final products. The possible formation mechanisms for products with diverse architectures have been presented in detail. Additionally, we systematically investigate the luminescent properties of the YVO4:Ln3+ (Ln = Eu, Dy, Sm, and Er). Because of an efficient energy transfer from vanadate groups to...
TL;DR: It is suggested that RuPOP may be a candidate for further evaluation as a chemopreventive and chemotherapeutic agent for human cancers, especially for melanoma.
Abstract: The limitations of cisplatin-based chemotherapy, including high toxicity, undesirable side effects, and drug resistance, have motivated extensive investigations into alternative metal-based cancer therapies Ruthenium (Ru) possesses several favorable properties suited to rational anticancer drug design and biological applications In the present study, we synthesized a series of ruthenium polypyridyl complexes containing N,N-chelating ligands, examined their anticancer activities, and elucidated the molecular mechanisms through which they caused the cancer cell death The results demonstrated that [Ru(phen)2-p-MOPIP](PF6)2·2H2O (RuPOP), a complex with potent antiproliferative activity, is able to induce mitochondria-mediated and caspase-dependent apoptosis in human cancer cells On the basis of these results, we suggest that RuPOP may be a candidate for further evaluation as a chemopreventive and chemotherapeutic agent for human cancers, especially for melanoma
TL;DR: A series of five isostructural tetranuclear lanthanide complexes of formula (mdeaH(2) = N-methyldiethanolamine; piv = pivalate; Ln = Tb (1), Dy (2), Ho (3), Er (4), and Tm (5) have been synthesized and characterized and have a planar "butterfly" Ln(4) core.
Abstract: A series of five isostructural tetranuclear lanthanide complexes of formula [Ln4(μ3-OH)2(mdeaH)2(piv)8], (mdeaH2 = N-methyldiethanolamine; piv = pivalate; Ln = Tb (1), Dy (2), Ho (3), Er (4), and Tm (5)) have been synthesized and characterized. These clusters have a planar “butterfly” Ln4 core. Magnetically, the LnIII ions are weakly coupled in all cases; the Dy4 compound 2 shows Single Molecule Magnet (SMM) behavior.
TL;DR: The hybrid PW(x)/MIL-101 materials were stable to leaching, behaved as true heterogeneous catalysts, were easily recovered by filtration, and reused several times with the maintenance of the catalytic performance.
Abstract: Polyoxotungstates [PW4O24]3− (PW4) and [PW12O40]3− (PW12) have been inserted into nanocages of the metal organic framework MIL-101. The hybrid materials PWx/MIL-101 (x = 4 or 12) containing 5−14 wt % of polyoxotungstate have been obtained and characterized by elemental analysis, N2 adsorption, FT-IR, Raman, and 31P NMR MAS spectroscopic techniques. Their catalytic performance was assessed in the selective oxidation of alkenes with aqueous hydrogen peroxide under mild reaction conditions ([H2O2] = 0.1−0.2 M, 50 °C, MeCN). PWx/MIL-101 enclosing 5 wt % of polyoxotungstate demonstrated fairly good catalytic activities in the epoxidation of various alkenes (3-carene, limonene, α-pinene, cyclohexene, cyclooctene, 1-octene), the turnover frequencies (TOF) and alkene conversions were close to the corresponding parameters achieved with homogeneous PWx. For the oxidation of substrates with aromatic groups (styrene, cis- and trans-stilbenes), a higher level of olefin conversion was attained using PW12/MIL-101. Moreo...
TL;DR: The results showed that true blue emission and short turn-on time is achieved when an ionic conductor, tetrabutylammonium trifluoromethanesulfonate, was used as the matrix for the film containing the emitters.
Abstract: A new series of cationic blue-emitting, heteroleptic iridium(III)-based metal complexes were systematically synthesized using two 4,6-difluorophenylpyridine ligands as well as one methyl- or n-butyl-substituted bisimidazolium salt carbene-type ligand. In degassed CH2Cl2, all complexes display highly efficient, blue phosphorescence (λmax ∼ 452 nm; emission quantum yield ∼ 0.30) at room temperature and also show blue emission in a thin film. The measured photophysical properties of the complexes have been rationalized with the help of quantum-chemical calculations. Because of the high solubility of the complexes, solution-processed devices, light-emitting electrochemical cells (LEECs), were made. The results showed that true blue emission and short turn-on time is achieved when an ionic conductor, tetrabutylammonium trifluoromethanesulfonate, was used as the matrix for the film containing the emitters. These iridium complexes and the described devices are the bluest materials ever reported and the first cas...
TL;DR: A fluorescent Zn(2+) sensor 2-(hydroxymethyl)-4-methyl-6-((quinolinyl-8-imino)methyl)phenol (HMQP) based on the 8-aminoquinoline platform has been synthesized and shows high selectivity, sensitive fluorescence enhancement, strong binding ability, and ratiometric response to Zn (2+) in Tris-HCl (50 mM, pH 7.54).
Abstract: A fluorescent Zn2+ sensor 2-(hydroxymethyl)-4-methyl-6-((quinolinyl-8-imino)methyl)phenol (HMQP) based on the 8-aminoquinoline platform has been synthesized. This sensor displays high selectivity, sensitive fluorescence enhancement, strong binding ability, and ratiometric response to Zn2+ in Tris−HCl (50 mM, pH 7.54), THF−H2O (9:1, v/v). And an obvious color change between HMQP and Zn2+−MQP− can be visually observed by the naked eye. The composition of the complex Zn2+−MQP− has been found to be 1:2 based on the fluorescence/absorption titration and further confirmed by X-ray crystallography.
TL;DR: It is shown that so far only the double-hybrid density functional B2PLYP, in conjunction with large and flexible basis sets (def2-QZVPP), is able to provide qualitatively correct results of spin-state energetics for the investigated non-spin-crossover complexes.
Abstract: The energies of different spin multiplicities of a range of iron complexes are computed using modern density functional theory (DFT) methods of the generalized gradient approximation (GGA; BP86 and OPBE), meta-GGA (TPSS), hybrid meta-GGA (TPSSh), hybrid (B3LYP), and double-hybrid (B2PLYP) types It is shown that so far only the double-hybrid density functional B2PLYP, in conjunction with large and flexible basis sets (def2-QZVPP), is able to provide qualitatively correct results of spin-state energetics for the investigated non-spin-crossover complexes An energy difference of -6 to 0 kcal/mol is proposed to be indicative of spin-crossover behavior
TL;DR: A novel template- and surfactant-free low temperature solution-phase method has been successfully developed for the controlled synthesis of ultrathin SnO(2) single-crystalline nanorods, offering a new material form for sensors, solar cells, catalysts, water treatments, and other applications.
Abstract: A novel template- and surfactant-free low temperature solution-phase method has been successfully developed for the controlled synthesis of ultrathin SnO(2) single-crystalline nanorods for the first time. The ultrathin SnO(2) single-crystalline nanorods are 2.0 +/- 0.5 nm in diameter, which is smaller than its exciton Bohr radius. The ultrathin SnO(2) nanorods show a high specific area (191.5 m(2) g(-1)). Such a thin SnO(2) single-crystalline nanorod is new in the family of SnO(2) nanostrucures and presents a strong quantum confinement effect. Its formation depends on the reaction temperature as well as on the concentration of the urea solution. A nonclassical crystallization process, Ostwald ripening process followed by an oriented attachment mechanism, is proposed based on the detailed observations from a time-dependent crystal evolution process. Importantly, such structured SnO(2) has shown a strong structure-induced enhancement of gas-sensing properties and has exhibited greatly enhanced gas-sensing property for the detection of ethanol than that of other structured SnO(2), such as the powders of nanobelts and microrods. Moreover, these ultrathin SnO(2) nanorods exhibit excellent ability to remove organic pollutant in wastewater by enormous surface adsorption. These properties are mainly attributed to its higher surface-to-volume ratio and ultrathin diameter. This work provides a novel low temperature, green, and inexpensive pathway to the synthesis of ultrathin nanorods, offering a new material form for sensors, solar cells, catalysts, water treatments, and other applications.
TL;DR: The new luminescent PMMA-doped Eu(CPFHP)(3)(DDXPO) complex shows considerable promise for polymer light-emitting diode and active polymer optical fiber applications.
Abstract: A novel efficient antenna complex of Eu3+ [Eu(CPFHP)3(DDXPO)] supported by a highly fluorinated carbazole-substituted β-diketonate ligand, namely, 1-(9H-carbazol-2-yl)-4,4,5,5,5-pentafluoro-3-hydroxypent-2-en-1-one (CPFHP) and the 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide (DDXPO) ancillary ligand, has been synthesized, structurally characterized, and its photoluminescent behavior examined. The single-crystal X-ray diffraction analysis of Eu(CPFHP)3(DDXPO) revealed that this complex is mononuclear, and that the central Eu3+ ion is surrounded by eight oxygen atoms, six of which are provided by the three bidentate β-diketonate ligands. The remaining two oxygen atoms are furnished by the chelating phosphine oxide ligand. The coordination polyhedron is best described as that of a distorted square antiprism. The photophysical properties of Eu(CPFHP)3(DDXPO) benefit from adequate protection of the metal by the ligands with respect to non-radiative deactivation as well as an efficient ligand-to-metal ...
TL;DR: The origin of the dielectric transition is attributed to the dynamics of the DMA cations: above 190 K these cations can rotate inside the cubooctahedral cavity created by the [Mn(HCOO)(3)](-) framework, while for lower temperatures such rotation gets frozen, and their cooperative arrangement inside the cavities give rise to the observed dielectrics transition.
Abstract: We have found that the hybrid organic-inorganic perovskite-like formate Mn(HCOO)(3)[(CH(3))(2)NH(2)] shows a dielectric transition around 190 K. According to single crystal X-ray diffraction, the compound shows rhombohedral symmetry at room temperature and monoclinic symmetry at low temperature (100 K), and the main difference between both structures is that the (CH(3))(2)NH(2)(+) (DMA) cations are disordered in the high temperature phase but cooperatively ordered in the low temperature one. The vibrational spectra of this compound reveal that significant changes take place in the vibrations ascribed to the DMA cation (changes in the frequency of certain vibrations, splitting of particular vibrations, and changes in the intensities), while no significant changes have been observed in those attributed to the formate anion. On the basis of all this information, we attribute the origin of the dielectric transition to the dynamics of the DMA cations: above 190 K these cations can rotate inside the cubooctahedral cavity created by the [Mn(HCOO)(3)](-) framework, while for lower temperatures such rotation gets frozen, and their cooperative arrangement inside the cavities give rise to the observed dielectric transition.
TL;DR: Increased long-term performance was found for photocatalytic H(2) production in a homogeneous combination of [Re(NCS)(CO)(3)bipy] (1; bipy = 2,2'-bipyridine), [Co(dmgH)(2) = dimethylglyoxime), triethanolamine (TEOA), and [HTEOA][BF(4)] in N,N-dimethylformamide.
Abstract: Increased long-term performance was found for photocatalytic H2 production in a homogeneous combination of [Re(NCS)(CO)3bipy] (1; bipy = 2,2′-bipyridine), [Co(dmgH)2] (dmgH2 = dimethylglyoxime), triethanolamine (TEOA), and [HTEOA][BF4] in N,N-dimethylformamide, achieving TONRe up to 6000 (H/Re). The system proceeded by reductive quenching of *1 by TEOA, followed by fast (k1 = 1.3 × 108 M−1 s−1) electron transfer to [CoII(dmgH)2] and subsequent protonation (K2) and elimination (k3, second-order process in cobalt) of H2. Observed quantum yields were up to ∼90% (H produced per absorbed photon). The type of acid had a substantial effect on the long-term stability. A decomposition pathway involving cobalt is limiting the long-term performance. Time-resolved infrared (IR) spectroscopy confirmed that photooxidized TEOA generates a second reducing equivalent, which can be transferred to 1 (70%, k2e− = 3.3 × 108 M−1 s−1) if no [CoII(dmgH)2] is present.
TL;DR: All zinc complexes were shown to be very effective catalysts for the ring-opening polymerization (ROP) of lactides at ambient temperature, producing polymers with controlled and narrow molecular weight distributions.
Abstract: A series of chiral NNO-tridentate Schiff base ligands derived from natural amino acids were reacted with zinc(bis-trimethylsilylamide)2 to provide metal complexes which have been fully characterized. One of these derivatives was further reacted with p-fluorophenol to yield a phenoxide complex. X-ray crystallographic studies reveal the zinc Schiff base amide complexes to be monomeric, whereas, the p-fluorophenolate complex was shown to be dimeric with bridging phenoxide ligands. All zinc complexes were shown to be very effective catalysts for the ring-opening polymerization (ROP) of lactides at ambient temperature, producing polymers with controlled and narrow molecular weight distributions. These enantiomerically pure zinc complexes did not show selectivity toward either l- or d-lactide, that is, kd(obsd)/kl(obsd) ≈ 1. However, steric substituents on the Schiff base ligands exhibited moderate to excellent stereocontrol for the ROP of rac-lactide. Heterotactic polylactides were produced from rac-lactide wi...
TL;DR: In this Forum Article, the use of dioxygen (O(2)) in oxidations catalyzed by polyoxometalates is discussed based on the formation of a stable iron(III) hydroperoxide compound that may have implications for the oxidation of other lower-valent polyoxmetalates such as vanadium(IV)- and ruthenium(II)-substituted polyoxometricalates.
Abstract: In this Forum Article, we discuss the use of dioxygen (O2) in oxidations catalyzed by polyoxometalates. One- and two-electron-transfer oxidation of organic substrates is catalyzed by H5PV2Mo10O40 and often occurs via an outer-sphere mechanism. The reduced polyoxometalate is reoxidized in a separate step by O2 with the formation of water. H5PV2Mo10O40 also catalyzes electron transfer−oxygen transfer reactions. Here, in contrast to the paradigm that high-valent oxo species are often stronger oxygen-transfer species than lower-valent species, the opposite occurs. Thus, oxygen transfer from the catalyst is preceded by electron transfer from the organic substrate. The monooxygenase-type reduction of O2 with polyoxometalates is also discussed based on the formation of a stable iron(III) hydroperoxide compound that may have implications for the oxidation of other lower-valent polyoxometalates such as vanadium(IV)- and ruthenium(II)-substituted polyoxometalates. Finally, the formation of hybrid compounds through ...